Instrument for simultaneously measuring a succession of cylinder bores

ABSTRACT

A probe is an elongated tube with sensors positioned to match the cylinder bores with respect to number and distance apart and having radially projecting contact pins. When employed as intended, the probe rotates and slides back and forth in stationary bearings that are in turn accommodated in uprights in a stand. The probe extends through the bores of the work, which is precisely positioned between the uprights by the same bearings. A drive unit with a driveshaft in alignment with the probe and with motors that operate in conjunction with the latter to generate a translation and a rotation respectively is also mounted stationary in the stand independent of the aforesaid bearings. One end of the probe is coupled to the driveshaft such that it can neither rotate on nor slide axially along it by a universal joint that compensates within limits for angular error and radial shaft displacement.

BACKGROUND OF THE INVENTION

The invention concerns an instrument for simultaneously measuring asuccession of cylinder bores, especially the bores in the bearing lanesof motor blocks, cylinder heads, and similar structures, with respect toshape and alignment.

An instrument of this type and for this purpose is known from the salesliterature PAT MULTI-INCOMETER. The instrument is a mobile piece ofequipment used to measure a succession of bores like the bores in acrankshaft bearing lane for roundness, geometrical defects, andalignment. It has a probe that operates in conjunction with two motorsand a drive mechanism, generating a rotary motion and an axial motion,that is provided with heads associated with the bores in the work thatare to be measured with respect to number and position, and that extendswhen employed as intended through the bores. The probe rotates andslides back and forth in bearings at each end. The bearings can besecured to the particular face of the work by a universal suspension,allowing angular error in the faces of the work to be compensated forwithin design-dictated limits. The drive unit that the end of the probeextends through is flanged to one of these bearings.

The known instrument has been proven outstanding for measuring bearinglanes that have large-measure bores and/or are not too long. For verylong bore lanes and/or small-diameter bores on the other hand there isan unacceptable risk of contaminated results because the drive unitflanged like a projecting collar onto one of the probe's bearings exertsbending moments on the probe that can distort it in ways difficult tocorrect for.

SUMMARY OF THE INVENTION

The object of the present invention is accordingly to so improve aninstrument of the aforesaid type and for the aforesaid purpose that anyincorrect results deriving from flections in the probe will at least beextensively reduced and that even very long bore lanes and/or bores withshort diameters can be precisely measured.

This object is attained in accordance with the invention in aninstrument for simultaneously measuring a succession of bores withrespect to shape and alignment in that a probe is an elongated tube withsensors positioned to match the cylinder bores with respect to numberand distance apart and having radially projecting contact pins, in that,when employed as intended, the probe rotates and slides back and forthin stationary bearings that are in turn accommodated in uprights in astand and extends the bores in the work, which is precisely positionedbetween the uprights by the same bearings, in that a drive unit with adriveshaft in alignment with the probe and with motors that operate inconjunction with the latter to generate a translation and a rotationrespectively is also mounted stationary in the stand independent of theaforesaid bearings, and in that one end of the probe is coupled to thedriveshaft such that it can neither rotate on nor slide axially along itby a universal joint that compensates within limits for angular errorand radial shaft displacement.

Considering the operational relationship between the probe and the driveunit's driveshaft by way of a universal joint that compensates withindesign-dictated limits for angular error and radial shaft displacementbetween the driveshaft and the probe, the instrument in accordance withthe invention incorporates a drive mechanism that is practically free oftransverse forces for a probe that is also mounted completelyindependent of the drive unit.

To promote the desired adaptability of the instrument to variousconditions the universal joint is rigidly secured to the takeoff end ofthe driveshaft in the drive unit and the probe is coupled to theuniversal joint, in such a way that it cannot rotate on or slide alongit but can be released from it, by a clutch. The clutch can be acompression clutch with a slotted compression ring that has acylindrical accommodation for one of the probe's insertion pins and thatcan be radially tensioned by a screw.

In spite of the practical absence of transverse forces on its drivemechanism, the probe can still bend under its own weight when it is verylong or when it is designed for measuring cylinder bores with shortdiameter. This problem is addressed in one advanced embodiment of theinvention in that an adapter that projects out of the end of the proberemote from the drive unit and has a prescribed and variablecounterweight can be fastened to that end such that it can neitherrotate on nor slide along it in order to apply a bending moment to theprobe that will compensate for any flections due to the probes ownweight.

The bearings at each end of the probe in another advanced version of theinvention can be removed from their associated uprights in the stand andreplaced. It is in this case practical for each bearing in the probe tobe associated with a supporting disk that is in turn accommodated in ahigh-precision bore that extends all the way through its upright in thestand and that it can be removed from and replaced in. Replacement isaccordingly simplified to replacing the disks that the bearings areassociated with.

The bearings at each end of the probe can be friction bearings that arenot as wide as their diameter and that have bores that expand toward thefaces of the bearings. They can alternatively be self-aligning bearings.

Given that the instrument in accordance with the invention is intendedfor measuring short-diameter cylinder bores, it is of advantage for thesensors to be integrated into the probe, with only the points of thecontact pins extending radially beyond its surface.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the instrument in accordance with the invention willnow be described with reference to the schematic drawings, wherein

FIG. 1 is an overall perspective view of an instrument for measuring thebearing bores in a bearing lane in the cylinder head, schematicallyrepresented by the dot-and-dash lines, of an internal-combustion engine,

FIG. 2 is a front view of the instrument with the work also representedby dot-and-dash line,

FIG. 3 is a top view of the instrument illustrated in FIG. 2,

FIG. 4 is a detail of the area IV in FIG. 2 where the probe is rigidlysecured to the driveshaft of a drive unit that is in turn securelyflanged to an upright by a universal joint illustrated in section,

FIG. 5 is a section along the line V--V in FIG. 4 through the probe andthrough the vicinity of the clutch's slotted compression ring that canbe radially tensioned with a screw to couple the probe to the driveshaftin the drive unit such that it can be uncoupled therefrom, and

FIG. 6 is a magnified longitudinal section through the probeillustrating a sensor with a radially moving contact pin.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An instrument 10 illustrated in its entirety in FIGS. 1 through 3comprises a stand consisting of a base plate 11 that accommodates threeuprights 12 and 13. Flanged securely onto outer upright 12 is a driveunit 15 with a driveshaft 16 that extends through the uprights. A probe18 is mounted in alignment with driveshaft 16 in bearings 17 in the twouprights 13 such that it can rotate and slide back and forth. Probe 18is coupled to the driveshaft such that it cannot rotate on or slidealong it but can be released from it by a universal joint 20.

The driveshaft 16 in drive unit 15 can rotate and move back and forthaxially and operates in conjunction with two motors 21 and 22, whichgenerate a rotation and a translation respectively. The probe 18 that issecurely coupled to and can be released from the driveshaft has sensors24 positioned to match the cylinder bores with respect to number anddistance apart. The sensors have contact pins 26 with points 25 thatproject radially beyond the surface of the probe.

When the instrument is employed as intended, work 28 is positionedprecisely between uprights 13 with the bearings 17 that accommodateprobe 18 in a known way in that index pins 30 on positioning blocks 29engage indexing bores introduced into the work from one end of the uppermount. The particular work is a cylinder head with a succession ofmutually separated bearing bores, through which the probe, equipped withsensors 24 equal in number and distribution extends.

Universal joint 20, which ensures transmission free of transverse forcesof the motion of the driveshaft 16 in drive unit 15 to probe 18, ismounted on the takeoff end of the driveshaft that extends through theouter upright 12 in the stand that the drive unit is rigidly flanged to.Universal joint 20 comprises a inner ring 32 that is loosely mounted onthe takeoff end of the driveshaft by radial entraining pins 33. Theentraining pins engage radial bores in the driveshaft and are secured byworm screws screwed into threaded bores that extend in from the face.

The sections of entraining pins 33 that extend beyond the driveshaftengage radial bores in inner ring 32 that are provided with bearingbushings 34. The inner ring of the universal joint can accordingly,since it is loosely mounted on the driveshaft, execute limited radialmotions in relation to the driveshaft. Inner ring 32 is also looselysurrounded by an outer ring 35, and the two rings are fastened togethersuch that they cannot rotate or slide in relation to each other byentraining pins 36 that are rotated 90° in relation to the aforesaidentraining pins 33. Entraining pins 36 are securely accommodated inradial bores in inner ring 32 and further secured by worm screws screwedinto threaded bores in the face. The radial bores in outer ring 35 arealso equipped with bearing bushings 37. The entraining pins and thebearing bores, lined with their bushings, in the inner and outer ringsaccordingly constitute friction bearings that allow, to the extentpermitted by the play between driveshaft 16 and inner ring 32 on the onehand and between inner ring 32 and outer ring 35 on the other hand,radial motions and limited rotations o the part of the rings in relationto each other. The universal joint will accordingly not only compensatefor angular error but will also accommodate radial shaft displacement.

A probe 18 can be coupled to the driveshaft 16 in drive unit 15 whendesired by means of a clutch 40 with a sleeve 41 that is secured at thetakeoff end to the outer ring 35 of universal joint 20 by a pin 42accommodated in axial recesses and by screws 43 distributed over thecircumference. A tensioning ring 44 extends from the clutch sleeve tothe end facing away from universal joint 20. Tensioning ring 44 has acylindrical accommodation 45 for the coupling pin of the particularprobe 18 being coupled and a radial slot extending separatedapproximately 180° from the sleeve as well as in its vicinity and can beradially tensioned across the screw 47 extending to the slot by atensioning lever 48. Between sleeve 41 and the outer ring 35 onuniversal joint 20 is an entraining disk 50 with an entrainer thatpositively engages a recess in the face of the pin on the particularprobe being employed.

The bearings 17 at each end of probe 18 are friction bearings. Eachcomprises a bearing bowl 52 with a bore that tapers out to each end anda supporting disk 54 that securely accommodates the particular bowl.Tensioning rings 44 themselves are interchangeably accommodated inprecision recesses 56 aligned with the axis of the driveshaft 16 indrive unit 15 in the uprights 13 in the stand that demarcate each sideof a work holder and are secured by threaded connections 57 on eachupright. The instrument can be easily refitted by replacing the probealong with the bearings at each end and the supporting disks thataccommodate them. As previously mentioned herein, probe 18 is equippedwith sensors 24 that match the cylinder bores being measured in numberand distance apart. The sensors are completely integrated into theprobe, with only the points 25 of the radially movable contact pins 26projecting beyond its surface. FIG. 6 illustrates one of the sensors,all of which are identical in design. The sensor is an insert 60 thatfits into a transverse recess in probe 18 and matches its outer surface.A leaf spring 61 provided with expansion strips is tensioned into oneend of a threaded inner securing block 62 in insert 60. Contact pin 26acts on the free end of the spring. The point 25 of the contact pinprojects radially beyond the surface of the probe and moves back andforth in a positioning bushing 64 that is screwed into the insert. Thesection 65 of the contact pin that engages the free end of the spring isconvex. The lines 66 illustrated in FIG. 6 extend through the tubularprobe 18 and transmit signals in a known way in accordance with theparticular deflection of the leaf spring 61 in each sensor, a procedurethat will not be described in detail herein.

FIGS. 2 and 3 illustrate how an adapter 70 with a counterweight 71 ismounted on the end of probe 18 that faces away from drive unit 15. Thepurpose of the counterweight is to at least partly compensate forflections that occur in the probe between the bearings 17 at each enddue to the probe's own weight by subjecting it to a prescribed bendingmoment.

The embodiment of the instrument in accordance with the inventiondescribed herein by way of example is employed to measure bearing boresfor the camshaft bearings in the cylinder heads of internal-combustionengines. When the instrument is employed as intended, the work isaccommodated on positioning blocks 29 between the uprights 13 thataccommodate the bearings 17 at each end of the probe and positionedcorrectly by the index pins 30 that engage indexing bores in the work.Probe 18 will then extend through the axially separated bearing bores inthe work. The contact pins 26 in sensors 24 will then be in the vicinityof the bores being measured. The bores are measured by sensing a seriesof adjacent inside circumferences. The probe is for this purpose rotatedby a motor 21 in drive unit 15 and another motor 22, a stepper, in thedrive unit advances it along the axis of the bore after eachcircumference has been sensed.

What is claimed is:
 1. An instrument for simultaneously measuring asuccession of cylinder bores with respect to shape and alignment,particularly bores in bearing lanes of motor blocks, cylinder heads, andsimilar structures of a workpiece, comprising: a probe with an elongatedtube and sensors positioned to match the cylinder bores with respect tonumber and spacing and having radially projecting contact pins;stationary bearings held in uprights in a stand, said probe rotating andsliding back and forth in said stationary bearings and extending throughbores in the workpiece, said workpiece being substantially preciselypositioned between said uprights by said bearings; a drive unit with adrive shaft in alignment with said probe; motors in said drive unit andoperating in conjunction with said probe to generate translational androtational motion, said drive unit being mounted stationary in saidstand independent of said bearings; a universal joint coupling one endof said probe to said drive shaft and preventing said probe fromrotating on said shaft and sliding axially along said shaft, saiduniversal joint compensating for angular error and radial shaftdisplacement within limits.
 2. An instrument as defined in claim 1,wherein said universal joint is rigidly secured to a takeoff end of saiddriveshaft in said drive unit; and clutch means for releasing said probefrom said universal joint, said probe being coupled to said universaljoint so that said probe cannot rotate on said joint or slide along saidjoint but can be released therefrom by said clutch means.
 3. Aninstrument as defined in claim 2, wherein said clutch means comprises acompression clutch with a slotted compression ring having a cylindricalaccommodation for one of said contact pins of said probe; and screwmeans for radially tensioning said compression ring.
 4. An instrument asdefined in claim 10, including an adapted projecting out of an end ofsaid probe remote from said drive unit and having a predetermined andvariable counterweight, said adapted being fastened to said end of saidprobe so that said adapter can neither rotate on said probe nor slidealong said probe to applying a bending moment to said probe forcompensating against deflections due to own weight of said probe.
 5. Aninstrument as defined in claim 1, wherein said bearings are located ateach end of said probe and are removable from respective uprights andreplaced in said stand.
 6. An instrument as defined in claim 5,including a supporting disk associated with each bearing in said probeand located in a substantially high-precision bore extending entirelythrough its respective upright in said stand, said supporting disk beingremovable and replaceable.
 7. An instrument as defined in claim 5,wherein said bearings are located at each end of said probe and arefriction bearings, said bearings being less wide than their diameter andhaving bores expanding toward faces of said bearings.
 8. An instrumentas defined in claim 5, wherein said bearings comprise self-aligningbearings.
 9. An instrument as defined in claim 1, wherein said sensorsare integrated into said probe, said contact pins having points onlyextending radially beyond a surface of said probe.